Implementations of the present invention relate to methods of designing and fabricating support structures for overhang geometries of parts produced using additive manufacturing.
Powder-based electron beam additive manufacturing (EBAM) is an additive manufacturing (AM) technology by which physical solid parts are made, layer-by-layer, directly from electronic data. The electronic data is generally provided in files from computer-aided design (CAD) software. EBAM utilizes a high-energy electron beam, as a moving heat source, to melt and fuse metallic powders and produce parts in a layer-wise fashion. Powders made of other materials may also be used in the process.
If a part has overhang geometry, such as a cantilevered overhang or undercut portion, defects such as curling may occur due to the thermal gradient cycles that lead to high thermal stresses and geometric deformation. FIG. 1A illustrates a CAD model of a part 10 having two overhang portions 11, 12, and FIG. 1B illustrates the part 10 fabricated using EBAM without a support structure and curling at the end of the overhang portions 11, 12.
A current practice for countering this curling effect is to build a support structure with the part that connects the overhang portion with the support structure. In particular, the geometry of the support structure is incorporated in the part model (CAD format) and becomes solid from metallic powders during the EBAM process, connecting the support structure to the overhang portion. FIG. 2A illustrates an example of a typical lattice support design 20a, 20b for upper and lower overhang portions, respectively. Although the support structure 20a, 20b may eliminate the part deformation problem, the support structure 20a, 20b is bonded to the part and needs to be removed in post-processing using a mechanical tool, typically. This process is laborious, time consuming, and degrades the surface quality of the cantilevered portion. FIG. 2B shows support structure 20b mostly removed from the example part.
Accordingly, improved methods and articles of manufacture are needed to reduce labor and time required for fabrication and to improve the quality of the part.